1. Field of the Invention
The present invention relates to a composition in the form of an oil-in-water (O/W) emulsion containing a high content of wax and to the use thereof in the cosmetics and dermatological fields, in particular in caring for, treating and/or making up the skin and/or mucous membranes, and more particularly in the treatment of wrinkles and/or fine lines of the skin and/or in the treatment and/or protection of dry skin.
The invention also relates to a process for the preparation of such a composition, wherein at least one stage of the process is carried out using a mixer-extruder.
2. Discussion of the Background
It is known to use waxes in cosmetic creams in the form of emulsions and which are used in the care of human skin, and, in particular, for the antiwrinkle effects contributed by these waxes. Nevertheless, it is difficult to incorporate a high percentage of waxes in these compositions because waxes have a tendency to greatly thicken emulsions. In addition, when a high percentage of waxes is incorporated in an emulsion, the emulsion is very difficult to apply to the skin because it does not slip. Furthermore, a rough effect is produced on the skin. Such an emulsion is therefore of no practical use.
Furthermore, it is also known to incorporate a high percentage of waxes in mascaras. However, compositions of this type cannot be used as a care product because of the above-mentioned disadvantages.
Furthermore, in order to prepare an emulsion containing waxes, it is necessary to melt the waxes in the fatty phase of the emulsion, and in particular if it is desired, for example, to use waxes, such as carnauba waxes, which are particularly advantageous because of their antiwrinkle effect on the skin. In so doing, it is therefore necessary to heat the fatty phase to 80-85xc2x0 C., which is particularly harmful when it is desired to introduce heat-sensitive compounds thereto.
A need therefore remains for a composition containing a significant percentage of waxes without the above disadvantages.
Accordingly, it is an object of the present invention to provide an O/W emulsion having a high wax content therein.
It is also an object of the present invention to provide a process for preparing an O/W emulsion having a high wax content therein.
It is, moreover, an object of the present invention to provide a method of treating mammalian skin, mucous membranes and/or hair using an o/w emulsion having a high wax content therein.
The above object and others are provided by a composition in the form of an oil-in-water (O/W) emulsion, containing an oily phase dispersed in an aqueous phase, which contains a mixture of at least two nonionic emulsifiers, the mixture being liquid at ambient temperature and having an HLB ranging from about 6 to 13, and wherein the oily phase contains at least about 5% by weight of one or more waxes based on the total weight of the composition, at least one of the waxes having a starting melting temperature of greater than or equal to about 50xc2x0 C.
Quite surprisingly, it has now been discovered, in accordance with the present invention, that it is possible to incorporate a high percentage of waxes in O/W emulsions, while retaining satisfactory fluidity and a pleasant feeling during application on the skin, by preparing the emulsion under cold conditions using a mixture of nonionic emulsifiers, which is liquid at ambient temperature and which has an appropriate HLB (HLB=Hydrophilic Lipophilic Balance), and starting from a soft oily phase containing a high percentage of waxes.
The present invention thus provides a composition in the form of an oil-in-water emulsion containing an oily phase dispersed in an aqueous phase, which contains a mixture of at least two nonionic emulsifiers, the mixture being liquid at ambient temperature and having an HLB ranging from about 6 to 13, and wherein the oily phase contains at least about 5% by weight of one or more waxes based on the total weight of the composition, at least one of the waxes being a wax having a starting melting temperature of greater than or equal to about 50xc2x0 C.
The composition obtained, although containing a high level of wax, is fresh on application.
The present inventors have particularly sought to avoid the use of ionic emulsifiers, which can be irritating to some skin types, notably to sensitive skin. However, the use of nonionic emulsifiers presents difficulties as there exists no nonionic emulsifier which is liquid at ambient temperature and which has an HLB ranging from about 6 to 13 which makes it possible to achieve the purpose and effect of the prevent invention. The present inventors have surprisingly discovered the effectiveness of using a mixture of nonionic emulsifiers.
The mixture of nonionic emulsifiers which is used in accordance with the present invention must be liquid at ambient temperature, that is to say at a temperature ranging from about 15xc2x0 C. to 25xc2x0 C., and have an HLB ranging from about 6 about to 13. It can contain in particular (1) at least one nonionic emulsifier having an HLB equal to or greater than about 13, and (2) at least one nonionic emulsifier having an HLB equal to or less than about 5. In addition, it can optionally contain at least one coemulsifier which may in particular be necessary if the emulsifiers (1) and (2) used are both solids, the coemulsifier then being liquid and making it possible to obtain a liquid mixture.
As is known, the HLB of a mixture of emulsifiers corresponds to the mean of the HLB values of each of the emulsifiers constituting the mixture, taking into account the proportion by weight of these emulsifiers.
Mention may be made, as nonionic emulsifiers with an HLB equal to or less than 5, of, for example, esters of polyols and of a fatty acid having an alkyl chain containing from 12 to 22 carbon atoms, such as esters of fatty acid and of glycerol, of glucose or of sorbitol; oxyethylenated derivatives of esters of polyols and of a fatty acid having an alkyl chain containing from 12 to 22 carbon atoms, which derivatives contain from 1 to 50 oxyethylene groups, such as a complex of triisostearin (triester of glycerol and of isostearic acid) and of PEG-6; ethers of polyethylene glycol and of a fatty alcohol having an alkyl chain containing from 12 to 22 carbon atoms, which ethers contain from 1 to 50 oxyethylene groups, such as oleyl ethers and in particular oleth-25 (25 oxyethylene groups), and their mixtures.
Use may advantageously be made, as nonionic emulsifiers with an HLB equal to or less than about 5, of those which are liquid at ambient temperature, such as polyol fatty esters and fatty ethers with a branched or unsaturated chain containing from 12 to 22 carbon atoms and, in particular, sorbitan monoisostearate, such as the product sold under the name xe2x80x9cArlacel 987xe2x80x9d by the company ICI, sorbitan mono/dioleate, such as the product sold under the name xe2x80x9cArlacel 83xe2x80x9d by the company ICI, the complex of triisostearin and of PEG-6, such as the product sold under the name xe2x80x9cLabrafil isostearicxe2x80x9d by the company Gattefossxc3xa9, decaglyceryl pentaisostearate, such as the product sold under the name xe2x80x9cNikkol Decaglyn 5-ISxe2x80x9d by the company Nikko Chemical, or methyl glucose dioleate, such as the product sold under the name xe2x80x9cIsolan DOxe2x80x9d by the company Goldschmidt.
Mention may be made, as nonionic emulsifiers with an HLB equal to or greater than about 13, of, for example, esters of polyethylene glycol and of a fatty acid having an alkyl chain containing from 12 to 22 carbon atoms, which esters contain from 5 to 100 and preferably from 20 to 60 oxyethylene groups, such as PEG-40 stearate; ethers of polyethylene glycol and of a fatty alcohol having an alkyl chain containing from 12 to 22 carbon atoms, which ethers contain from 5 to 100 and preferably from 10 to 30 oxyethylene groups, such as ceteareth-25 or ceteth-25; esters of sorbitan and of a fatty acid having an alkyl chain containing from 12 to 22 carbon atoms, which esters comprise from 0 to 100 and preferably from 4 to 25 oxyethylene groups, such as polysorbate 20, polysorbate 40 and polysorbate 60; esters of sugar and of a fatty acid having an alkyl chain containing from 12 to 22 carbon atoms, such as sucrose stearate; derivatives of polyethylene glycol and of esters of glycerol and of a fatty acid having an alkyl chain containing from 12 to 22 carbon atoms, such as PEG-8 caprylic/capric glycerides; polyethylene glycol ethers of esters of methyl glucose and of a fatty acid having an alkyl chain containing from 12 to 22 carbon atoms, such as PEG-20 methyl glucose sesquistearate; and their mixtures.
Use may advantageously be made, as nonionic emulsifiers with an HLB equal to or greater than about 13, of those which are liquid at ambient temperature, such as polysorbate 20, for example the product sold under the name xe2x80x9cTween 20xe2x80x9d by the company ICI, polysorbate 40, for example the product sold under the name xe2x80x9cTween 40xe2x80x9d by the company ICI, PEG-8 caprylic/capric glycerides, for example the product sold under the name xe2x80x9cLabrasoll, by the company Gattefossxc3xa9, or PEG-20 methyl glucose sesquistearate, for example the product sold under the name xe2x80x9cGlucamate SSE 20xe2x80x9d by the company Amerchol.
Mention may be made, as a coemulsifier, of, for example, fatty alcohols containing a branched or unsaturated chain having from 8 to 22 carbon atoms, such as isostearyl alcohol; fatty acids containing a branched or unsaturated chain having from 8 to 22 carbon atoms, such as ricinoleic acid; esters of a polyol and of a branched fatty acid containing from 8 to 22 carbon atoms, such as branched fatty esters of glycerol or of propylene glycol, for example glyceryl isostearate or propylene glycol isostearate, and their mixtures.
Mention may be made, as a mixture of nonionic emulsifiers, which is liquid at ambient temperature and which has an HLB of 6 to 13, which can be used in the composition according to the invention, of, for example, the mixture of glyceryl stearate, propylene glycol stearate, glyceryl isostearate, propylene glycol isostearate, oleth-25 and ceteth-25 sold by the company Gattefossxc3xa9 under the name xe2x80x9cHydrolactol 70xe2x80x9d, with an HLB of 10.
The amount of mixture of emulsifiers (emulsifiers and coemulsifier) in the composition according to the invention generally ranges from about 0.1 to 30% by weight of active material, and preferably from about 1 to 25% by weight of active material with respect to the total weight of the composition. The proportion of each emulsifier in this amount of emulsifiers can be easily determined by a person skilled in the art for the purpose of obtaining a mixture suitable for the criteria defined above. Preferably, the amount of nonionic emulsifiers, without taking into account the coemulsifier, ranges from about 0.5 to 10% by weight and preferably from about 0.5 to 5% by weight with respect to the total weight of the composition.
The composition of the present invention contains, in the oily phase, at least about 5% by weight of one or more waxes with respect to the total weight of the composition. The cooled oily phase oily phase, before it is mixed with the aqueous phase, advantageously exists in the form of a soft paste. The term xe2x80x9csoft pastelxe2x80x9d is understood here to mean a paste for which the viscosity can be measured, in contrast to the solid structure of a tube or stick, for which the viscosity cannot be measured. The dynamic viscosity of the soft paste at 25xc2x0 C. is generally between 3 and 35 Paxc2x7s, measured with a Contraves TV rotary viscometer equipped with an xe2x80x9cMS-r4xe2x80x9d rotor at a frequency of 60 Hz.
Mention may be made, as waxes which can be used in the composition of the invention, of, for example, mineral waxes, such as microcrystalline waxes, paraffin wax, petrolatum wax, petroleum wax, ozokerite or montan wax; animal waxes, such as beeswax, lanolin and its derivatives; vegetable waxes, such as candelilla, ouricurry, carnauba or japan waxes, cocoa butter, or cork fibre or sugar cane waxes; hydrogenated oils which are solid at 25xc2x0 C. fatty esters and glycerides which are solid at 25xc2x0 C.; synthetic waxes, such as polyethylene waxes and waxes obtained by the Fischer-Tropsch synthesis; silicone waxes, and their mixtures.
According to the present invention, use is made of at least one wax having a starting melting temperature greater than or equal to about 50xc2x0 C. and preferably at least one wax for which the starting melting temperature is greater than about 65xc2x0 C., such as carnauba wax, some polyethylene waxes and some microcrystalline waxes, such as that sold by the company Tisco under the name xe2x80x9cTisco Wax 88xe2x80x9d or that sold by the company RMC under the name of xe2x80x9cFeruwax 30540xe2x80x9d.
The term xe2x80x9cstarting melting temperaturexe2x80x9d is understood to mean, in the present description, the temperature at which a wax begins to melt. This temperature can be determined by DTA (differential thermal analysis), which makes it possible to obtain a thermogram (or melt curve) of the wax under consideration. The starting melting temperature corresponds to the temperature at which a significant change of slope in the thermogram can be observed. The melting point, for its part, represents the minimum point in the said thermogram.
The amount of wax(es) in the composition of the invention is at least about 5% and preferably ranges from about 5 to 30%, and preferably from about 5 to 15% by weight with respect to the total weight of the composition.
The amount of oily phase in the composition of the invention generally ranges from about 10 to 70%, and preferably from about 20 to 50% by weight with respect to the total weight of the composition. This oily phase is used in such an amount or else comprises an amount of waxes such that the amount of waxes in the final composition is equal to or greater than about 5%.
The oily phase of the composition of the invention generally comprises, in addition to the wax or waxes, one or more fatty substances chosen from oils of animal origin, oils of vegetable origin, mineral oils, synthetic oils, fluorinated oils, silicone oils, in particular volatile silicone oils, silicone gums, silicone resins, fatty alcohols, fatty acids and silicone elastomers, such as the products sold under the name xe2x80x9cKSGxe2x80x9d by the company Shin-Etsu, under the name xe2x80x9cTrefilxe2x80x9d, by the company Dow Corning or under the name xe2x80x9cGransilxe2x80x9d by the company General Electric.
The composition according to the present invention can advantageously also contain one or more fillers (pulverulent constituents) which can be, for example, talc; micas of natural or synthetic origin; kaolin; zinc or titanium oxides; calcium carbonate; magnesium carbonate and hydrocarbonate; silica, in particular spherical silica, silica powder, sold under the name xe2x80x9cCab-O-Sil TS 530xe2x80x9d by the company Cabot, and silica microbeads, such as those sold under the name SB150 by the company Myoshi; titanium dioxide; glass and ceramic beads sold by the company 3M under the trade name xe2x80x9cMacrolitexe2x80x9d; metal soaps derived from an organic carboxylic acid having from 8 to 22 carbon atoms, preferably from 12 to 18 carbon atoms, for example zinc, magnesium or lithium stearate, zinc laurate or magnesium myristate; powders formed from nonexpanded synthetic polymers, such as powders formed from polyethylene, polystyrene, polyesters, polyamides (for example, Nylon or poly-xcex2-alanine), acrylate copolymers (for example, the microporous microspheres sold by the company Dow Corning under the trade name xe2x80x9cPolytrapxe2x80x9d), poly(methacrylic acid)s, polystyrene or teflon, such as xe2x80x9cFluonxe2x80x9d; expanded powders, such as hollow microspheres made of thermoplastic material prepared by known processes, such as those disclosed in U.S. Pat. No. 3,615,972 and EP-A-056,219, and in particular the microspheres sold under the trade name xe2x80x9cExpancelxe2x80x9d by the company Kemanord Plast or under the trade name xe2x80x9cMicropearl F 80 EDxe2x80x9d by the company Matsumoto; powders formed from natural organic materials, such as maize, wheat or rice starches, which may or may not be crosslinked, such as the powders formed from starch crosslinked by octenylsuccinic anhydride sold under the name xe2x80x9cDry-Floxe2x80x9d by the company National Starch; silicone resin microbeads, such as those sold under the name xe2x80x9cTospearlxe2x80x9d by the company Toshiba Silicone, and their mixtures.
The fillers can represent up to about 20% by weight with respect to the total weight of the composition and preferably from about 1 to 12% by weight with respect to the total weight of the composition.
The aqueous phase of the composition of the present invention represents at least about 30% by weight with respect to the total weight of the composition and preferably from about 50 to 80% by weight with respect to the total weight of the composition.
The composition according to the present invention can be used in any field where this type of pharmaceutical dosage form is advantageous and in particular in the cosmetics and dermatological fields. When it constitutes a cosmetic and/or dermatological composition, it advantageously contains a physiologically acceptable medium, which is to say a medium which is compatible with the skin, mucous membranes, nails and/or hair.
The compositions which are the subject-matter of the present invention are applied in a large number of treatments of the skin, mucous membranes (lips) and hair, including the scalp, in particular in protecting, caring for, cleansing and/or making up the skin and/or so mucous membranes, in protecting, caring for and/or cleansing the hair and/or in the therapeutic treatment of the skin, hair and/or mucous membranes.
The compositions according to the present invention can be used, for example, as products for treating, caring for, protecting and/or cleansing the skin, in the form of creams or milks, or as (skin and lip) make-up products by incorporating fillers and/or coloring materials (pigments and/or dyes). They are particularly appropriate in the treatment of wrinkles and/or fine lines of the skin and in the treatment and/or protection of dry skin.
The present invention also provides for the cosmetic use of the composition as defined above in treating, protecting, caring for and/or cleansing the skin, mucous membranes and/or hair and/or in making up the skin and/or mucous membranes.
The present invention also provides for the cosmetic use of the composition as defined above in treating wrinkles and/or fine lines of the skin.
The present invention also provides for the use of the composition as defined above in the manufacture of a dermatological composition intended for treating and/or protecting dry skin.
In addition, the compositions of the invention can contain adjuvants which are conventionally used in the cosmetics or dermatological field, such as hydrophilic or lipophilic active principles, preservatives, antioxidants, fragrances, solvents, sunscreen agents, coloring materials, basic or acidic agents, and lipid vesicles. These adjuvants are used in the proportions which are conventional in the cosmetics or dermatological field, for example from about 0.01 to 30% of the total weight of the composition, and they are, depending in their nature, introduced into the aqueous phase or into the oily phase of the composition or alternatively into vesicles. These adjuvants and their concentrations must be such that they do not modify the property desired for the composition.
If it is desired to obtain a less fluid composition and/or to improve the stability of the emulsion, one or more hydrophilic gelling agents, such as carboxyvinyl polymers or carbomers and polyacrylamides, can be added thereto. According to a preferred embodiment of the invention, use is made of a polyacrylamide, such as the product sold under the name Hostacerin AMPS by the company Hoechst. These gelling agents are used at concentrations ranging from about 0.05 to 2%, preferably about 0.1 to 0.5%, by weight with respect to the total weight of the composition.
Mention may be made, as active principles which can be used in the composition of the invention, of, for example, moisturizing agents, such as polyols and in particular glycerol, ethylene glycol, isoprene glycol, 1,2-propanediol, diglycerol, sorbitol, polyethylene glycols and their mixtures.
The composition according to the present invention can advantageously be prepared by using, for at least one stage of the process, a kneading device, such as a roll-mill mixer comprising two rollers rotating in opposite directions, between which the paste passes, or a screw mixer-extruder. Use is preferably made of a screw mixer-extruder.
The present invention also provides for a process for the preparation of a composition according to the present invention, whereas at least one stage of the process is carried out using a screw mixer-extruder.
According to a first embodiment, the preparation process of the present invention entails comprises the following stages:
(1) preparation of the oily phase in the form of a soft paste obtained by forming a premix of the waxes and oils, by heating this premix to a temperature at which it melts, by then introducing the molten premix. and the other constituents (in particular the fillers) of the oily phase, all at once or in several portions, into a screw mixer-extruder subject to a temperature gradient ranging from 80xc2x0 C. to 20xc2x0 C., and by kneading the mixture obtained while cooling it to ambient temperature as it is conveyed to the outlet of the mixer-extruder;
(2) incorporation of the mixture of emulsifiers (emulsifiers and coemulsifiers) in the soft paste obtained in (1), and
(3) incorporation, with stirring, of the mixture obtained in (2) in the aqueous phase.
In this embodiment, stages (2) and (3) are carried out in a mixing device commonly used by a person skilled in the art, such as a rotor-stator.
In addition, in the process described above, the emulsifier used a mixture of nonionic emulsifiers, which is liquid at ambient temperature and which has an HLB of about 6 to 13, and the amounts used are such that the emulsion obtained comprises at least 5% of wax by weight with respect to the total weight of the composition.
As indicated above, as the mixing of the oily and aqueous phases takes place under cold conditions, the incorporation of heat-sensitive compounds is not problematic.
According to a specific embodiment of the invention, stages (2) and (3) above are also carried out in the screw mixer-extruder used for stage (1). The mixture of emulsifiers and the aqueous phase are then introduced into a part (or section) of the mixer-extruder where the temperature is close to ambient temperature.
The use of a mixer-extruder makes it possible to reproducibly obtain an oily phase paste of highly constant quality. Furthermore, it is possible, by adapting the outlet die of the mixer-extruder, to package the composition in line at the outlet of the said mixer-extruder.
The various stages of the process can be carried out in one or more extruders arranged one after the other and preferably in a single twin-screw extruder.
The conditions under which the extrusion can be carried out are known as described in FR-2515306, corresponding to U.S. Ser. No. 08/378,388, U.S. Pat. No. 6,120,781 which is incorporated herein in the entirety.